A US air strike on March 16 completely destroyed a building located next to an old mosque in the village of Al-Jineh in the northern province of Aleppo.
The Pentagon says the strike targeted a meeting of senior Al-Qaeda leaders but local reports and the Syrian Observatory for Human Rights monitoring group have claimed dozens of people were killed, including civilians.
Pentagon spokesman Navy Captain Jeff Davis told reporters that officials initially thought there were "zero" civilian casualties.
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After reviewing additional public and classified information over the weekend, Central Command has launched a casualty "credibility assessment" to determine whether allegations of civilian deaths have any merit.
"This is when there are allegations made about civilian casualties, they assess those allegations to determine if they are credible," Davis said.
"If they are determined to be credible, they take additional steps from there."
Questions have arisen over whether the targeted building was an annex to the mosque or somehow related.
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The US military is not supposed to strike or target mosques.
An AFP correspondent who visited the area Friday said there are two Omar bin al-Khattab mosques in Al-Jineh, adjacent to each other. The old one was damaged and the new one totally destroyed.
"Whether or not it was part of the mosque, I don't know," Davis said.
"But the main mosque we purposefully avoided and this was extensively surveilled prior to the strike that we did, and we are confident that we disrupted a significant meeting of senior Al-Qaeda leadership."
The Britain-based Syrian Observatory for Human Rights said on Friday that 49 people were killed -- most of them civilians.
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